For desktop computers, there are currently two standard sizes (width) for mass-storage drive units such as hard disc drives, floppy disc drives, CD-ROM drives, and tape drives; these two sizes of units are referred to as 5.25 inch (5"25) units and 3.5 inch (3"5) units. Standardising the size of such units, means that the mounting arrangements for the units need only be designed to receive particular sizes of unit which facilitates the design of the mechanical structure of a desktop computer. Thus, for example, a desktop computer may be designed with four drive bays, three of which are for 5"25 units and one for a 3"5 drive; whilst these drive bays can be populated with any desired units, a typical population would be a hard disc drive, CD-ROM drive and DAT tape drive for the 5"25 drive bays and a floppy disc drive for the 3"5 drive bay.
Traditionally, the mounting structure provided in a desktop computer for mounting drive units units has taken the form of a cage-like metal frame to which the units have been secured by fixing screws. To improve manufacturability, various other mounting structures have been used such as the structure described in U.S. Pat. No. 5,306,079 that provides a number of different drive bays.
To provide both the manufacturer and user with the flexibility to add optional units as needed, it is standard practice to provide several drive bays in a computer. The manufacturer populates the drive bays according to the version of the computer to be produced whilst a user can add additional units as desired. Because of the two different standard sizes of drive units, it is common to provide drive bays adapted for both sizes of units. Nevertheless, it frequently occurs that a desired drive unit cannot be added because although there is an unoccupied drive bay, it is of the wrong size. To ease this problem it is known to provide mounting adaption pieces that can adapt a 5"25 size drive bay to receive a 3"5 drive unit (because the reverse adaption is not possible, it is desirable to provide more 5"25 drive bays than 3"5 drive bays). The use of such adaption pieces is not, however, an ideal solution because they may need to be separately ordered by a user wanting to install a drive unit and are usually difficult to mount.
It is an object of the present invention to overcome the foregoing problem.